I often like alert better (osascript -e 'display alert "'"$1"'"'"), this way the message don't go away before you click ok.

Can also combine with a vocal message: sleep 2; osascript -e 'say "Hello World!"'; osascript -e 'display alert "hello world"'

The last one copied from https://code-maven.com/display-notification-from-the-mac-com...